Department of Anthropology, School of Anthropology and Conservation, University of Kent, Canterbury CT2 7NR, United Kingdom. n.von-cramon@kent.ac.uk

Abstract

Variation in the masticatory behavior of hunter-gatherer and agricultural populations is hypothesized to be one of the major forces affecting the form of the human mandible. However, this has yet to be analyzed at a global level. Here, the relationship between global mandibular shape variation and subsistence economy is tested, while controlling for the potentially confounding effects of shared population history, geography, and climate. The results demonstrate that the mandible, in contrast to the cranium, significantly reflects subsistence strategy rather than neutral genetic patterns, with hunter-gatherers having consistently longer and narrower mandibles than agriculturalists. These results support notions that a decrease in masticatory stress among agriculturalists causes the mandible to grow and develop differently. This developmental argument also explains why there is often a mismatch between the size of the lower face and the dentition, which, in turn, leads to increased prevalence of dental crowding and malocclusions in modern postindustrial populations. Therefore, these results have important implications for our understanding of human masticatory adaptation.

Shape changes on PC1 and PC2 (21.4% and 11.1% variance explained, respectively) associated with major differences in subsistence economy. Agriculturalist populations (open symbols) have relatively short and broad mandibles with a tall, angled ramus and coronoid process, whereas hunter-gatherer populations (closed symbols) have relatively long and narrow mandibles with a short, upright ramus and coronoid process.